A structure as shown in FIGS. 81A-81B is disclosed as one example of the prior art vibration gyro sensor. FIG. 81A is a perspective view. FIG. 81B is a schematic plan view. As shown in FIGS. 81A-81B, a vibrator 1 is disposed on abase plate or substrate 10. The vibrator 1 is supported from its both sides to beams 8 and mounted to the substrate 10 by anchors 13. Comb-toothed electrodes 9A and 9B are mounted to the vibrator 1. A comb-toothed driver electrode 2 is fixedly mounted to the substrate 10 at a space with the comb-toothed electrode 9B. Furthermore, a comb-toothed monitor electrode 3 is fixedly mounted to the substrate 10 at a space with the comb-toothed electrode 9A. The driver electrode 2 is an electrode for exciting the vibrator 1 to vibrate relative to the substrate 10. In this vibration gyro sensor, the vibrator 1 is excited to vibrate by an exciting AC voltage applied to the driver electrode 2. Comb-toothed movable electrodes 11A and 11B are mounted around the center of the vibrator 1. Comb-toothed fixed electrodes 12A and 12B are fixedly mounted to the substrate 10 at a space with the movable electrodes 11A and 11B (see, for example, JP-A-11-183178 and JP-A-2000-292174).
In the above-described vibration gyro sensor, the vibrator 1 is excited to vibrate in the illustrated X-direction by the driver electrode 2 and rotates about the Z-axis. A Coriolis force is produced in the Y-direction perpendicular to the direction of axis of rotation and to the direction of vibrations. The movable electrodes 11A, 11B and fixed electrodes 12A, 12B, forming a set, act as electrodes for detecting the Coriolis force in a corresponding manner to a variation in the capacitance between the movable electrodes 11A, 11B and the fixed electrodes 12A, 12B.
The following structure is disclosed as one example of electromagnetically driven angular velocity detector. The structure is equipped with a disk-shaped vibrating mass of silicon. The disk-shaped vibrating mass is joined to an underlying glass substrate at anchor portions at the four corners via 4 rectangular support springs. The support springs act also as electrode extraction leads extending from the disk-shaped vibrating mass that is a common movable electrode. The movable comb-toothed electrodes of an electrostatic actuator are mounted at four diametrically opposite locations on the outer periphery of the disk-shaped vibrating mass. Two fixed comb-toothed electrodes are fixedly mounted to the glass substrate oppositely to the four electrodes. An AC voltage is applied between the opposite fixed comb-toothed electrodes, giving reciprocating vibrations to the movable electrodes. Rotary vibration is induced in the central disk-shaped vibrating mass. A lower electrode for detecting a capacitance with the disk-shaped vibrating mass via a gap (space) is split into four sectors and mounted to the glass substrate (for example, see “Fundamental Researches on Rotational Vibration Gyroscope”, the Transactions of the Institute of Electrical Engineers of Japan, E, Vol. 119, August/September, 1999, written by Takayuki Fujita, Kenta Hatano, Takuya Mizuno, Ichisuke Maenaka, and Muneo Maeda).
In the above-described angular velocity detector, in a case where an angular velocity is detected, there is a danger that a detection electrode installed opposite to the vibrator is brought into contact with the vibrator by an external large shock. Therefore, insulative protrusions are mounted to the vibrator as a countermeasure to prevent damage to the vibrator when it is touched.
Another electromagnetically driven angular velocity detector has two rectangular vibrators consisting of thin silicon film. The vibrators are connected by a spring. The four corners of each connected vibrator are supported to a glass substrate by other four springs via pillars. Electrodes are disposed on the vibrators, respectively, to drive them electromagnetically. Extraction leads connected with the electrodes are mounted on the springs supported to the pillars. Counter detection electrodes are mounted in positions opposite to the vibrators via spaces to detect the capacitance.
A problem to be solved is that a large displacement cannot be had because of limitations on the operation of the comb-toothed electrodes in the case of the capacitance-detecting gyroscope using the comb-toothed electrodes. Therefore, limitations are placed on improvement of the detection sensitivity. It is impossible to set large the vibrating amplitude of the vibrating vibrations in order to set high the detection sensitivity. Furthermore, in detecting capacitance using comb-toothed electrodes, angular velocity only in one axial direction can be detected for structural reasons. Consequently, it is difficult to detect angular velocities in the two or more axial directions. In addition, where angular velocities around X- and Y-axes, respectively, are detected using a driving amplitude in the Z-axis direction, the gap between the vibrator and a detection electrode installed opposite to the vibrator needs to be set larger than the driving amplitude and so there is the anxiety that the detection sensitivity is deteriorated.